Just 15 years ago, the Zoo was chronically underfunded — but that was before a public-private partnership changed everything.

The year was 1920, and bison herds across America were growing once again.

Before European settlers began moving westward across the plains, an estimated 30 to 50 million bison roamed the country’s grasslands; by 1884, only 325 wild bison remained, their numbers decimated by years of relentless hunting. Up to that point, as many as 5,000 to 10,000 were being killed per day to keep up with international demand for bison bones and hides, while the U.S. government did little to protect the native species.

It took the creation of a public-private partnership, the American Bison Society, in 1905, to step in and defend the few bison left in one small portion of the country: Yellowstone National Park. Theodore Roosevelt acted as its honorary president. By 1920, thanks to the society’s work, more than 12,000 American bison roamed the plains once again. Soon, the herds needed thinning to ensure continued growth, and the U.S. government donated a few of those bison to young zoos across the country.

This is how the Houston Zoo came to receive its very first animal: Earl, the American bison. Earl was housed for a short time in Sam Houston Park alongside a deer who’d been brought in to keep him company before the two were moved to Hermann Park in 1922. And the Houston Zoo was born.

It would take another public-private partnership to come to the zoo’s own rescue 80 years later.

By 2002, our zoo had grown from its small, two-animal display into a 55-acre park that included everything from Asian elephants to komodo dragons, but it was also chronically underfunded. City Hall was responsible for what had become a $17 million annual budget, but the zoo was in great need of maintenance and repairs that had been deferred for decades.

Successful exhibits had opened in prior years. They were just bankrolled by private donations: the $7.5 million Wortham World of Primates, the $1.2 million renovation of the Janice Seuber McNair Asian Elephant facility, the $6.5 million John P. McGovern Children’s Zoo. Which is why zoo officials had begun to wonder if a steady stream of private funds might provide a path toward a brighter, sustainable future.

In July 2002, with the blessing of the city, the Houston Zoological Society became the non-profit corporation Houston Zoo Inc., assuming day-to-day operations and maintenance of the zoo while the city continues to own the land. A newly installed board began to tackle private fundraising efforts while creating a laundry list of projects that needed their attention. By 2010, an institution that had once struggled to attract talented staff and focus on educational programs had added $40 million in capital improvements. Five years later, more than 500 additional improvement projects had been completed to the tune of $125 million, almost all of it generated by private citizens through various galas and events.

People really want this city to be fantastic, and they want to do good. The growth we’ve seen is unprecedented in any other zoo in the nation.

“It’s almost a competitive sport in some ways, but in a good way,” chuckles Houston Zoo CEO Lee Ehmke, chatting about the surprising volume of donations that have rolled into the zoo in the last 15 years. “This is a community that does that better than anybody.”

Today, the Houston Zoo is even able to help other, smaller associations across the world—which it does generously, raising its own profile and attendance in the process.

The attraction of public-private partnerships is simple: Many donors feel more comfortable funneling their funds into a non-profit with a singular mission than they do taking their chances by donating money to a government-run organization whose budget (and staff) could easily be cut to make up for shortfalls in other areas—say, city pensions or property taxes. It’s attractive for institutions like the Houston Zoo, too, which can securely raise money knowing that they retain ultimate control over how and when it’s spent.

And while this type of arrangement is not a uniquely Houston phenomenon—the majority of the 232 Association of Zoos & Aquariums–accredited institutions in the U.S. have also transformed into public-private partnerships—perhaps no city does these partnerships better than the famously philanthropic Bayou City.

“People really want this city to be fantastic, and they want to do good,” says Ehmke, who’s been blown away by the generosity of Houstonians since moving here a year ago. “The growth we’ve seen is unprecedented in any other zoo in the nation.”

Ehmke arrived here from the Minnesota Zoo. Formerly an attorney practicing environmental law, he went back to graduate school at UC Berkeley to study landscape architecture in hopes of learning how to better design animal habitats for the zoos that had fascinated him since childhood. Not surprisingly, the Houston Zoo’s game-changing lowland gorilla exhibit—a $28 million undertaking that opened in 2015—was one of the things that attracted his interest in the job.

“Not only is it a state-of-the-art habitat that presents them in the context of their natural environment,” says Ehmke, who worked on a similar project at the Bronx Zoo, “it implicitly sends the message to people that if you want to have gorillas, you have to protect their habitat.” Among his many plans in the coming years, Ehmke wants to create more exhibits like that one to further the zoo’s educational goals. The lowland gorilla exhibit, he says, “tells stories about what the zoo is doing in terms of field conservation and support, where they’re working to save gorillas in the Congo, and tells people what they can do to help.”

To that end, Ehmke counts among his plans a redesigned entrance in which sea turtles are on display in a brand-new habitat that explains to visitors how the Houston Zoo is participating in conservation efforts in the Galapagos Islands. He wants to thin the zoo’s own herd, bringing in fewer animals in the future while creating larger, more technologically advanced habitats for those that remain. And he wants more zoo-goers to understand just how much wildlife protection work his staff is doing worldwide—and not only the keepers and veterinarians.

Unique among its peers, the Houston Zoo has actively searched for ways to get its entire staff involved in conservation efforts. Its accounting team has helped train the folks at Conservation Heritage–Turambe in Rwanda on using QuickBooks; its facilities employees (specifically its welders) have helped the team at Painted Dog Conservation in Zimbabwe create better tracking collars for African painted dogs in an effort to protect them from poachers; the PR squad has provided the partners at Grevy’s Zebra Trust in Kenya with website and newsletter development.

Back home, the zoo has treated over 400 sea turtles since 2010 in its vet clinic, preparing them to be reintroduced into Galveston Bay, and its outreach staff has assisted the U.S. Fish and Wildlife Department in saving the Attwater’s prairie chicken and the Houston toad. The graphic design team, meanwhile, is working on conservation efforts with Texas Black Bear, creating the same sort of signage that shares stories with Houston Zoo guests when they visit—which, by the way, they’re doing in record numbers.

Last year, the Houston Zoo hit a milestone: over 2.55 million visitors packed the park in 2016, making it the No. 1 attraction in Houston and the No. 2 most-visited zoo in the country, right behind the prestigious San Diego Zoo. Ehmke, who’s becoming well-acquainted with his new hometown, laughs of the attendance numbers: “I knew it was a big deal when we beat the Houston Livestock Show and Rodeo.”

And Ehmke says this is just the beginning. The Houston Zoo is hard at work on a master plan to create even more opportunities for learning and, hopefully, greater wildlife protection efforts. “More and more, we want to tell the story about all this conservation work that we’re doing—a storyline that links back to what we’re doing with our partners in the wild,” says Ehmke, who knows there’s still much work to be done. Although the Houston Zoo is now the top attraction in the city, he says, “We’ve still got more people to get here.”